New interface for the protocol plugin (WIP)

[FinnStutzenstein]

For testing, you need to run yarn as well as pip and check out this branch for OpenSlides as long it isn't merged.

TODOS:

• More filter options in create protocol view
• Include users into the protocol (which users?)
• Squash migrations
• PDF export of the protocol
• Inline editing for the detail containers
• "Insert all agenda items"-button